In recent years, a stereoscopic display device, which achieves stereo vision by spatially separating a plurality of images with binocular parallax into right and left eyes respectively, by using a lenticular lens, a parallax barrier and the like, is focused on as a stereoscopic display device using a flat-panel display such as a liquid crystal panel. This kind of stereoscopic display device is advantageous in that there is no need to wear special glasses (Non-patent Document 1, for example).
To generate a stereoscopic image for enhancing effect of the stereoscopic vision, there is disclosed a method of displaying the stereoscopic image by transforming an image, using a perspective projection, toward an oblique direction with respect to a visual axis (Patent Document 1). FIG. 5 is a diagram for explaining a method to generate a stereoscopic image. In the method for generating a stereoscopic image shown in FIG. 5, images corresponding to respective viewpoints of right eye 121 and left eye 122 are transformed by the perspective projection into a right eye perspective projection transformation image 123 and a left eye perspective projection transformation image 124, to be projected on the image display surface 125. In that case, the right eye perspective projection transformation image 123 and the left eye perspective projection transformation image 124 are projected, in the oblique direction with respect to the view axis, on the image display surface 125. When the stereoscopic display is performed using the above method, an observer perceives a stereoscopic image 126. At this time, each part of the projected image of the stereoscopic image 126 has different distance from an observing point of the observer in the image display surface 125, therefore the observer does not become conscious of the image display surface. It is effective to reduce eye strain of the observer caused by binocular stereo vision. In addition, a wide angle of view, which can be obtained by the above method, further enhances effect of the stereoscopic vision. As a result, a more realistic stereoscopic image can be provided.
FIG. 6 is a diagram illustrating a stereoscopic display device in which two or more image display elements are connected. In order to provide a stereoscopic display device having a wider angle of view by using image display elements 130 and 131, two or more image display elements 130 and 131 need to be connected so that the angle θ between the image display elements 130 and 131 becomes more than 90 degrees and less than 180 degrees. The stereoscopic image display elements 130 and 131 display a right eye perspective projection transformation image 132 and a left eye perspective projection transformation image 133 thereon, where the images are observed by an observer with his/her right eye 134 and left eye 135 at these respective viewpoints. As a result, the observer can observe a stereoscopic image 139 at wide angle of view, which leads to observation of a realistic stereoscopic image.
Non-patent Document 1: “Three-dimensional Image Engineering” by Takanori Okoshi, Asakura Publishing Co., Ltd. P. 11-21
Patent Document 1: U.S. Pat. No. 6,389,236
Patent Document 2: Japanese Patent Application Laid-open No. 2004-054193
Patent Document 3: Japanese Patent Application Laid-open No. 2001-305312